1. Field of the Invention
The present invention relates to an inverse telecine conversion apparatus, for use in a recording apparatus using an MPEG (Moving Picture Expert Group) encoding technique such as a DVD (Digital Versatile Disk) recorder, which converts moving television pictures simulated from cine-frame images into the original cine-frame images.
2. Description of Related Art
Moving pictures of a cinematic film that are cinematic materials are displayed on a screen with 24 frames per second of display information shown continuously over time.
On the other hand, moving television pictures which are television materials are displayed with 30 frames of image information (hereinafter “frame image information”) per second, continuously over time on a display. As shown in FIG. 1, top field image information 81 and bottom field image information 82 are combined with each other and scanned over, thereby defining frame image information 80.
When television video moving pictures (30 frames per second) are to be created from a cinema film (24 cine-frames per second), because of the difference in the number of images per second as described above, a conversion method such as that shown in FIG. 2 (hereinafter “telecine conversion”) is customarily used. That is, cine-frame image information is replaced with top field image information (the top ones of video fields shown in FIG. 2) or bottom field image information (the bottom ones of the video fields shown in FIG. 2). In addition, repeat field image information is inserted for every five pieces of the field image information. As the repeat field image information, there are two types, i.e., one that immediately precedes top field image information (the field image information two pieces back) is repeated as the top field image information again and the other that immediately precedes bottom field image information (the field image information two pieces back) is repeated as the bottom field image information again. In the following, moving television picture information created in such a manner from a cinema film will be referred to as “a pseudo moving television picture information.”
Incidentally, DVD is becoming increasingly popular at a rapid pace these days. This has made it necessary, for creation of DVD moving picture software (video contents) from conventional pseudo moving television picture information, to delete repeat field image information which is contained in pseudo moving television picture information and to convert it back into image information that is 24 cine-frames per second (hereinafter referred to as “inverse telecine conversion”). The reason is as described below.
1) While DVD requires the compression (encode) of image information, compression efficiency is better if pseudo moving television picture information is compressed after converting the pseudo moving television picture information back into cinema moving picture information at 24 cine-frames per second not including redundant information than if pseudo moving television picture information of at frames per second is compressed as it contains repeat field image information, and therefore, picture quality is better even when the volume of data is the same.
2) During frame-by-frame reproduction with a DVD reproducing apparatus (player), it is possible to reproduce a cinematic film frame by frame.
FIG. 3 is a drawing conceptually describing inverse telecine conversion in a conventional inverse telecine conversion apparatus. As shown in FIG. 3, pseudo moving television picture information (video frame: 30 frames/sec) telecine converted from a cinematic film is supplied to the inverse telecine conversion apparatus, repeat field image information is deleted as denoted by the dotted frame shown in FIG. 3, and the pseudo moving television picture information is converted into image information reproducing the original 24 cine-frames/sec cinema film.
Further, at the same time, control flags which are necessary for re-conversion of the 24 cine-frames/sec image information into 30 frames/sec moving television picture information are generated and added. In FIG. 3, a control flag TFF triggers an operation that top field image information is processed with priority within a frame with the control flag TFF. Meanwhile, a control flag BFF triggers an operation that bottom field image information is processed with priority within a frame with the control flag BFF. A control flag RFF triggers an operation that the first filed image information of a frame with the control flag RFF serves as repeat field image information.
As described above, since repeat field image information which is inserted during conventional inverse telecine conversion has a fixed cycle and a fixed position, utilizing this, inverse telecine conversion is realized with a method (hereinafter “constant cycle field deletion method”) that “deletes field image information which is at a certain fixed position for every five fields.”
Incidentally, a television program is broadcasted with TV commercials (CM) and announcements for other programs, which are originally television materials, inserted within a cinema film which originally is a cinematic material. That is, in general, a mixture of television materials and cinematic materials are broadcasted within a series of programs. Where a program in which images which originally are video materials and images which originally are cinematic materials are mixed with each other is to be recorded with a recording apparatus which uses an MPEG encoding technique such as a DVD recorder, since a conventional inverse telecine conversion apparatus assumes that entered moving television picture information is all cinematic material, the conventional inverse telecine conversion apparatus deletes a field representing a true frame image which should not be deleted instead of deleting a supplementary field which is contained in pseudo moving television picture information, or deletes fields at a constant cycle even if the fields are originally television materials. Thus, there is a problem that the compression efficiency when compressing MPEG images or picture quality deteriorates due to the deletion of information which should be left undeleted.